1. Field of the Invention
This invention relates generally to an apparatus for mounting through an aperture in a panel where the apparatus is configured to contain an object, such as a sound-emitting transducer. The invention relates more specifically to a cap for the apparatus, where the cap is configured to rotate to modify the volume of the sound passing through the apparatus.
2. Description of the Related Art
There are many fasteners that are capable of fastening two or more structures together. The conventional wood or metal screw has helical threads around a shaft, and the threads seat against the inwardly facing wall of an aperture formed in the structures. As the screw shaft is rotated, the screw head is displaced closer to one side of the structures to fasten them together. Alternatively, a nut and bolt can be used to fasten two or more objects together when the shaft of the bolt is inserted through an aperture in the objects and the bolt's head seats against the object on one end of the aperture and the nut seats against the object on the opposite end of the aperture. Upon tightening of the nut relative to the bolt, the interposed objects are fastened together.
One difficulty with a conventional nut and bolt is that it often takes numerous rotations of the nut relative to the bolt to tightly interpose the structure between the head and nut. Furthermore, if carried out by hand, these numerous rotations may consume time unnecessarily or cause repetitive-motion injuries, such as carpal-tunnel syndrome.
Various attempts have been made to solve these problems. U.S. Pat. No. 5,304,022 to Huska shows a bolt with a tapered shaft and a nut with engaging pitched threads on portions of the radially inwardly facing surface of the nut. Non-threaded portions of the radially inwardly facing surface of the nut are formed between the threaded portions of the nut, and a non-threaded portion of the bolt's shaft are formed between threaded portions. This configuration permits the nut to be slid onto the shaft for a part of the shaft's length.
U.S. Pat. No. 763,210 to Schwamberger and U.S. Pat. No. 5,980,177 to Schiess et al., disclose similar nut and bolt fasteners in which a nut is rapidly slid onto the bolt's shaft and then rotated to engage pitched threads. Such devices have the disadvantage that they still require some rotation. An additional disadvantage is that the pitch and coarseness of the threads must be such that the fastener can be tightened on opposite sides of the structures on which it is attached within the partial rotation permitted before the threads disengage. Otherwise, the fasteners will disengage without being sufficiently tightened.
U.S. Pat. No. 4,990,044 to Kimak is directed to a push-on fastener in which a nut has threaded structures that can be displaced radially away from a threaded shaft to permit the nut to slide over the bolt's threads. The nut is pushed as far as desired, and then threaded the remainder of the way. A disadvantage of such a device is that the tightening force on the nut also tends to displace the threaded structures radially, thereby permitting the nut to back off and loosen the fastener. Thus, any over-tightening might cause the nut to come loose over time, especially in an environment in which there is vibration.
One particular use for the above-described fasteners is as a housing for a sound-emitting transducer, such as a piezoelectric alarm or chime. Such transducers must often be mounted through an aperture formed in a panel, such as an elevator control panel, an automobile dashboard panel, or other structure. Conventional piezoelectric transducers, such as those offered and sold by Floyd Bell, Inc., have a circular cylindrical housing that contains the circuitry and a diaphragm that vibrates upon the actuation of the piezoelectric transducer. The housing has a helically-threaded male tip that extends through the aperture in the panel. A helically-threaded female collar fits onto the threading of the tip and tightens the housing against the back of the panel in the manner of a nut and bolt.
Conventional fasteners and housings have drawbacks that should be overcome to decrease the time required for installation, reduce repetitive-action injuries, improve the appearance of the finished product and decrease the likelihood of vibrating loose. Furthermore, such housings need volume-adjustment capability. Conventional housings have shutters with apertures that can be aligned with apertures in the housing. Sound waves can pass through the apertures when they are aligned, and are restricted when the apertures are not aligned.
Conventional volume-adjustment shutters have a fastener, such as a rivet or screw, that extends through the shutter and into the housing. The shutter rotates around the fastener in order to align and adjust the position of the apertures in the shutter relative to the apertures in the housing. However, such a structure has disadvantages, such as the need for an extra part (the fastener), the need for another hole in the housing for the fastener to pass through, and difficulty in removing the shutter once the fastener is in place. Finally, it is possible for fasteners such as screws to vibrate loose, thereby causing the shutter to fall off.
There is a need for a shutter and housing having a structure that overcomes these problems.